JN0-106 Junos OS Fundamentals Practice Questions

Question 1

A Juniper device is experiencing high CPU utilization due to a routing protocol process. The engineer suspects a specific BGP peer is causing the issue. Which operational command can be used to collect diagnostic information about the routing protocol processes?

Accepted Answer

show system processes extensive. 'show system processes extensive' displays detailed CPU and memory usage for each individual process, including routing protocol daemons like bgpd. This allows the engineer to see which routing protocol process (e.g., bgpd) is consuming excessive CPU resources. However, it does not identify a specific BGP peer; further investigation with commands like 'show bgp neighbor' would be needed to isolate the peer.

Answer

request support information

Answer

show bgp summary

Answer

monitor traffic interface

Question 2

Which TWO statements are true about the Junos OS candidate configuration model? (Choose two.)

Accepted Answer

The candidate configuration can be modified without affecting the active configuration.. The Junos OS candidate configuration model allows modifications to be made to a separate candidate configuration file without affecting the active configuration currently running on the device. This ensures that changes can be staged, reviewed, and validated before being committed, providing a safe and non-disruptive way to manage configuration changes.

Answer

Each change is applied incrementally to the active configuration.

Answer

The candidate configuration is stored in a separate file from the active configuration.

Answer

After a commit, the candidate configuration is automatically discarded.

Question 3

Which THREE commands are valid Junos operational mode commands for monitoring network diagnostics? (Choose three.)

Accepted Answer

traceroute. The 'traceroute' command in Junos operational mode sends a series of UDP packets with increasing TTL values to discover the path a packet takes to a destination, which is a standard network diagnostic tool. It is a valid operational mode command used for monitoring network connectivity and path analysis.

Answer

show configuration

Answer

request system reboot

Question 4

Which TWO statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)

Accepted Answer

It validates the candidate configuration for syntax errors.. The 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.

Answer

It schedules the configuration to be applied at a later time.

Answer

It discards the candidate configuration after saving.

Answer

It automatically reboots the device to apply the changes.

Question 5

You are a network engineer at a service provider. You have a Juniper MX router that serves as a BGP route reflector for a large number of customer routes. Recently, the router has been experiencing high CPU utilization, and the BGP process (rpd) is consuming excessive memory. You suspect that the router is receiving too many routes from a specific BGP peer, causing the routing table to grow beyond the available memory. You need to diagnose the issue without affecting production traffic. Which course of action should you take?

Accepted Answer

Use the 'show bgp summary' command to check the number of prefixes per peer.. The 'show bgp summary' command displays the number of prefixes received from each BGP peer, allowing you to identify which peer is advertising an excessive number of routes. This directly addresses the suspicion of a specific peer and is non-disruptive to production traffic.

Answer

Immediately shut down all BGP peers to stop the influx of routes.

Answer

Configure a prefix limit on all BGP peers.

Answer

Use the 'show route summary' command to check the routing table size and memory usage.

Question 6

A network engineer notices that a Junos device is not forwarding traffic for a specific subnet. The routing table shows the route for that subnet, but traffic is still not being forwarded. Which command should the engineer use to verify whether the firewall filter is dropping the traffic?

Accepted Answer

show firewall filter. To verify whether a firewall filter is dropping traffic, you need to inspect the packet counters for each filter term. The command 'show firewall filter' displays all firewall filter statistics, including packet/byte counts for terms with a discard action, allowing you to see if the drop counter is incrementing. 'show firewall filter log' is not a standard Junos command; the correct command for logs is 'show firewall log', and logs are only generated if the filter term explicitly includes a 'log' action. Therefore, the correct answer is C, not D.

Answer

show interfaces terse

Answer

show firewall filter counter

Answer

show firewall filter log

Question 7

Which THREE of the following statements are true regarding Junos OS commit operations?

Accepted Answer

The 'commit check' command validates the candidate configuration without activating it.. Option A is correct because 'commit check' performs a syntax and semantic validation of the candidate configuration against the schema without making it the active configuration, so errors are reported but nothing is activated. Option B is correct because the 'commit' command merges the candidate configuration into the active configuration and activates it on the device. Option C is correct because 'commit confirmed' activates the candidate configuration but starts a rollback timer (default 10 minutes); if the operator does not issue a confirming 'commit' before the timeout, Junos automatically reverts to the previous active configuration. Option D is not marked correct because although Junos supports commit scripts, they are configured and executed as part of the commit process rather than being run multiple times arbitrarily during a single commit. Option E is not marked correct because 'rollback' reverts the candidate configuration to a previously committed configuration (rollback 0 being the current active one), not to the current active configuration itself.

Answer

You can run multiple commit scripts during a single commit operation.

Answer

The rollback command reverts to the current active configuration.

Question 8

Refer to the exhibit. An engineer wants to verify that static routes for 10.0.1.0/24 and 10.0.2.0/24 are present in the routing table. Based on the output, which statement is true?

Accepted Answer

Both routes are active and have the same preference value.. The output shows both 10.0.1.0/24 and 10.0.2.0/24 as static routes with a preference of 5. Since the preference value is the same and both are listed as active (the 'A' flag is present in the routing table), both routes are installed and active in the forwarding table. In Junos, a static route's default preference is 5, and any route with a lower preference is preferred; here both have equal preference, so they coexist as active routes.

Answer

Both routes have a preference of 0.

Answer

Only the 10.0.1.0/24 route is active.

Answer

Both routes use the same next-hop IP address.

Question 9

A network engineer needs to check the operational status of all interfaces on a Juniper device. Which command provides a summary of interface status including link state, protocol state, and error counters?

Accepted Answer

show interfaces. The 'show interfaces' command provides a detailed summary of all interfaces, including administrative status, link state, protocol state, and error counters. It displays a comprehensive view of interface operational status, which meets the engineer's requirement for error counters. Option C (show interfaces terse) gives a concise summary but does not include error counters.

Answer

show configuration interfaces

Answer

show interfaces terse

Answer

show interface descriptions

Question 10

Refer to the exhibit. How many next hops are configured for the 192.168.1.0/24 route?

Accepted Answer

2. The route 192.168.1.0/24 has two next hops configured: one via 10.0.0.2 and another via 10.0.0.3. This is a case of equal-cost multipath (ECMP) routing, where Junos installs multiple next hops for the same prefix to load-balance traffic across multiple paths.

Answer

0

Answer

3

Answer

1

Junos OS Fundamentals

JN0-106 Junos OS Fundamentals — Key Topics

Where candidates lose marks on Junos OS Fundamentals